Gaseous fuel powered engines are common in many applications. For example, the engine of a locomotive can be powered by natural gas (or another gaseous fuel) alone or by a mixture of natural gas and diesel fuel. Natural gas may be more abundant and, therefore, less expensive than diesel fuel. In addition, natural gas may burn cleaner in some applications.
Natural gas has traditionally been introduced into an engine's cylinders via a solenoid operated admission valve. Although effective in some applications, a solenoid operated admission valve may not have the speed and/or force required to open fast enough or against high boost pressures in other applications.
One attempt to improve gas injection is disclosed in U.S. Pat. No. 5,996,558 of Ouellette et al. that issued on Dec. 7, 1999 (“the '558 patent”). In particular, the '558 patent discloses a hydraulic actuated gaseous fuel injector. The injector includes an oil inlet port, a gas inlet port, and a gas injection port. High-pressure oil is supplied to the oil inlet port from an in-line fuel injection pump. When the pump pressurizes the oil for injection actuation, a force is applied under a gas injection needle, causing the needle to lift away from and unblock the gas injection port. Once the needle is in an open position, fuel introduced via the gas inlet port is allowed to flow into a corresponding combustion chamber via the injection port. In some embodiments, an electronically controlled valve is used to regulate oil flow into and out of the injector.
Although the hydraulic actuated gaseous fuel injector of the '558 patent may be an improvement over a solenoid operated admission valve, the injector may still suffer drawbacks. For example, reliance on pump pressure to actuate the injector may require very precise pump control and such control may be complex and costly. In addition, a different pump may be required for each injector of a multi-cylinder engine. Further, the injector design shown in the '558 patent may lack broad applicability in engines having tight space constraints (e.g., in dual fuel engines).
The engine system of the present disclosure solves one or more of the problems set forth above and/or other problems in the art.